Glioma is the most common tumor of the central nervous system (CNS), with an annual incidence of approximately 6.4/100,000 [1]. The incidence of glioma in developed countries is increasing year by year for unknown reasons. CBTRUS (2008) [1] in the United States pooled and analyzed data on 73,583 cases of primary CNS tumors between 2000 and 2004, of which gliomas accounted for approximately 36% of all CNS tumors and 81% of malignant CNS tumors. The annual mortality and disability rates of gliomas remain chronically high. For example, the survival of patients with mesenchymal astrocytoma (WHO grade III) and glioblastoma multiforme (WHO grade IV) is less than 6 months without treatment, and the median survival after comprehensive treatment (surgery + radiotherapy + chemotherapy) is only about 1 year (WHO grade IV) and 2 years (WHO grade III), respectively. Surgical resection is the most critical first step in the comprehensive treatment strategy for glioma. The main objectives of surgery include: (1) radical resection of the tumor (e.g., hairy cell astrocytic glioma); (2) reduction of tumor size to create favorable conditions for adjuvant radiotherapy; (3) clarification of pathological diagnosis; (4) screening of chemotherapeutic agents; (5) reduction of intracranial pressure; and (6) relief of neurological deficits. Since the last decade, an increasing number of evidence-based medical findings have confirmed that – although multiple factors influence the survival of patients with glioma – the extent of tumor resection is one of the main reasons. The use of radical surgery to achieve total imaging resection of glioma lesions not only facilitates other comprehensive treatments, such as radiotherapy, chemotherapy or immunotherapy, but also effectively prolongs the time to tumor recurrence and patient survival, and helps improve the quality of patient survival after surgery. For example, Wirtz CR (2000) reported that the total resection rate of glioma was strongly correlated with the time to recurrence and survival after surgery, and Albert et al. (1994) demonstrated in a prospective study that the risk of death in cases with tumor remnants detected by early postoperative MRI in glioblastoma (GBM) was 6.595 times higher than that in cases without tumor remnants. There is controversy regarding low-grade gliomas, with the main focus on the biology of diffuse infiltration of gliomas and the high 5-year survival rate (requiring up to 10 years of prospective randomized controlled clinical trials to obtain level I evidence-based medicine). The 2008 US guidelines for the treatment of CNS tumors recommend that the first step in the treatment of both low-grade and high-grade gliomas is surgery to achieve maximal safe resection of the tumor. Early postoperative (<72 h) MRI review should be included as a standard measure to assess the extent of tumor resection. The evaluation criteria for total resection of glioma include: (1) total resection by the sarco-eye (or under the surgical microscope); (2) total resection by imaging; and (3) total resection by histopathology. Since gliomas are located in the brain parenchyma and grow diffusely and infiltratively, and lack histological boundaries that can be distinguished by the naked eye, the neurosurgeon's judgment of the extent of glioma resection during surgery relying only on experience and visual observation (total resection by the naked eye) is often inaccurate and generally does not exceed the imaging boundaries of the tumor. Therefore, despite advances in microsurgical techniques, early postoperative MRI review confirms that only about 60% of gliomas can be fully resected on imaging. The current hot spots in glioma surgery research are mainly focused on the development and clinical application of new techniques of image-guided surgery, including: conventional neuronavigation, functional neuronavigation, intraoperative imaging neuronavigation, intraoperative neurophysiological monitoring combined with neuronavigation and quantitative imaging analysis of the infiltrative border of glioma. Conventional neuronavigation The rate of brain tumor resection has been greatly improved by MRI image navigation. Depending on the imaging characteristics of different tumor types, different reference images for navigation are used. Generally, MRI T1W enhanced sequence images can be used to guide the scope of surgical resection for high-grade glioma, while MRI T2W or FLAIR sequence images can be used for low-grade glioma. Nearly 1,000 cases of glioma surgery have been completed by the Department of Neurosurgery of Huashan Hospital in the past ten years, and the follow-up data show that 82.7% of glioma cases can achieve total resection by imaging, and the postoperative disability rate of patients is 15.0%, with better clinical efficacy than non-navigation surgery cases. 2. Functional neurological navigation For glioma in superficial non-functional areas, radical resection should be pursued. However, for gliomas in functional areas, it is a clinical challenge to improve the extent of lesion resection while preserving neurological function. The application of multimodal image fusion technology, which allows the fusion of structural brain images with functional images (PET [19], BOLD [15, 20] or DTI [21]) to guide the surgical process of glioma, is called functional neuronavigation. Functional neuronavigation uses conventional MRI to reconstruct the cranial structure model, fMRI to localize the functional areas of the cerebral cortex, and DTI to display the subcortical nerve conduction tracts, respectively, to precisely locate the adjacent neurofunctional areas while clarifying the lesion boundaries, which helps to improve the lesion resection rate and avoid neurofunctional damage. Since 2001, based on conventional neuronavigation, our unit has been focusing on functional neuronavigation surgery for the treatment of glioma in the motor area. The results of a large-scale prospective clinical trial study completed over a period of 5 years have confirmed with evidence-based level I evidence that: (1) The new technique can increase the total surgical resection rate of motor zone glioma from 51.7% to 72.0% (close to the total resection rate of non-functional zone navigation surgery). (2) The immediate postoperative disability rate was reduced from 32.8% to 15.3% (comparable to that of non-functional area navigation surgery). (3) Patients' long-term quality of life also improved significantly, with KPS scores rising from 74 to 86. (4) The clinical study also demonstrated a significant independent survival benefit of the new functional neuronavigation technique, which reduced the risk of postoperative death by 43.0% in patients with malignant glioma of the motor region (WHO grade 3-4) compared to conventional navigation surgery. Functional neuronavigation surgery is also applicable to cortical language area and visual area glioma surgery. 3. Intraoperative imaging is the most important challenge for neuronavigation technology. The virtual anatomical space created by preoperative medical imaging data alone cannot accurately correspond to the actual anatomical structure of the brain tissue during surgery. In order to solve the error caused by brain displacement, the domestic units in clinical practice mainly adopt measures to reduce the degree of brain displacement by reducing cerebrospinal fluid loss and mitigating brain tissue traction. However, the effectiveness of these measures is poor and they cannot fundamentally solve the problem of brain displacement. The dynamic acquisition of intraoperative images is currently an effective solution to correct brain shift in real time. Commonly used intraoperative imaging techniques include (1) (B-type) ultrasound imaging techniques: although the intraoperative ultrasound technique is simple, its low resolution is its weakness [25]. (2) Intraoperative CT imaging techniques: although they have some ability to discriminate brain tissue, they are far inferior to MRI and the presence of X-ray radiation damage prevents them from being widely used [26]. (3) Intraoperative MRI (iMRI) is the most accurate and reliable solution for correcting brain shift during neuronavigation [27-33]. iMRI can dynamically scan during surgery, update navigation images in real time, correct brain shift errors, and precisely guide the surgical trajectory and resection range, thus achieving radical resection of glioma and Quantitative preservation of adjacent normal brain tissue. Since Alexander E first proposed the concept of iMRI in 1996 [34], this technique has been highly valued by the clinical neurosurgery community and has developed rapidly in just a decade. Our unit was the first to introduce the PoleStar? N20 low field intensity iMRI neuronavigation system in China in 2006. We have completed 198 cases of glioma resection with iMRI neuronavigation, and the results showed that the total resection rate of glioma was 90.5%, which was higher than that of conventional navigation (82.7%); the postoperative severe disability rate was 6.8%, which was lower than that of conventional neuronavigation (15.0%). Among the 81 patients with malignant glioma (WHO grade 3-4), the median survival time after surgery was 19.3 months for those with "total resection", which was higher than that for those with "non-total resection" (median survival time of 14.0 months), and the median survival time for those with "total The risk ratio for "total resection" vs. "non-total resection" = 0.468. i.e., increasing the rate of total glioma resection reduces the risk of postoperative death by 53.2%. iMRI neuronavigation surgery for glioma treatment has the following advantages: (1) Multi-sequence structural imaging allows accurate determination of the brain (1) Multi-sequence structural imaging can accurately determine the imaging boundary of glioma and the morphological structure of surrounding normal tissues. (2) iMRI intraoperative dynamic scanning updates the navigation images in real time and corrects brain shift errors. (3) Real-time quantitative monitoring of the extent of tumor resection. Black reported that in more than 1/3 of cases, the surgeon subjectively judged that the tumor was completely resected, but iMRI confirmed that there were still tumor remnants [28]. In our study, 42.9% of glioma cases [35] were found to have lesions that were not resected to the extent planned preoperatively by iMRI and required further surgical resection. (4) High safety The iMRI technique is free of ionizing radiation damage and is safe for both patients and surgeons. (5) It is suitable for multi-site, high- and low-grade gliomas. Therefore, OH et al. (2005) suggested that gliomas are the best indication for iMRI neuronavigation surgery [36]. 4. Intraoperative neurophysiological monitoring technique Also known as evoked potentials monitor (EPM), it is one of the important techniques for the surgical standardization of lesions in functional brain areas (including: motor, sensory and speech). Among them, intraoperative brain mapping can be accurately achieved by applying either intraoperative sensory evoked potentials (SEP) phase flip technique or motor evoked potentials (MEP). Direct cortical electrical stimulation is commonly used to localize the motor cortex and subcortical electrical stimulation to localize the subcortical motor conduction pathway, the pyramidal tract, in motor area gliomas. The anesthetic protocol should not interfere with the acquisition of adequate neural or myoelectric signals. Therefore intraoperative application of myoelectric drugs should be balanced between patient braking and obtaining a good signal/noise ratio. For patients undergoing general anesthesia, the MEP procedure requires that the degree of myorelaxation and EMG response can be monitored in real time using the train-of-four stimulation (TOF) method. New progress has also been made in the research of various methods to detect the depth of anesthesia based on EEG signal analysis, such as bispectral index (BIS) monitoring. For glioma surgery in the language area, arousal anesthesia combined with intraoperative neurophysiological monitoring can help preserve the function of the language cortex intraoperatively. SEP and cranial neurophysiological measurements, such as brainstem auditory evoked potentials (BAERs), are appropriate in brainstem glioma surgery.Legatt in 2002 surveyed the use of MEP in 57 neurosurgical units mainly in the United States and showed an overall success rate of 91.6%. In some patients at high risk for neurological impairment, the combined application of neuronavigation and intraoperative EPM can greatly improve the postoperative neurological preservation rate. Some new electrodes that can be used for EPM under neuronavigation are gradually entering the clinic. 5. Quantitative imaging analysis of the infiltrative border of glioma There is no medical imaging technique that can precisely outline the histopathological profile of glioma. Even for different pathological types or different grades of glioma, there is no definite study conclusion confirming the precise relationship between various imaging techniques used clinically and their histopathological borders. Therefore, the extent of resection of gliomas is often limited to the imaging borders rather than the histopathological borders. This also explains why tumors recur quickly even after total resection. Imaging studies of recurrent glioma cases show that more than 75% of recurrent foci are located within 2 cm of the primary foci, and distant recurrences are rare, accounting for about 1-5%. The tumor recurrence is mostly located around the primary foci, which is related to the high density of tumor cells around the tumor remnant cavity and the low density of tumor cells in the area far from the foci. Therefore, some scholars suggest that surgery for glioma needs to be expanded. However, what is the appropriate quantitative range of expansion? Determining the histopathologic extent of glioma is critical to the surgical planning of the tumor. Currently, the imaging methods used to determine the imaging boundaries of mesenchymal gliomas and glioblastomas (WHO grade III and IV) in neuronavigation surgery are mainly MRI T1W enhancement; while for imaging boundaries of diffuse gliomas (astrocytic or oligoblastic), the imaging methods are mainly MRI T2W or FLAIR imaging. In addition, some functional MRI techniques have been investigated in the subclinical field to quantify the imaging boundaries of gliomas. For example, MRS, DWI, PWI, and dynamic contrast-enhanced MRI. Ganslandt O et al. (2005) reported the use of MRS to quantify the infiltrative border of gliomas and the fusion of metabolic images of brain tissue with structural images, which was applied to navigated surgery of gliomas to achieve histopathological total resection of gliomas. In addition, photodynamic diagnosis and fluorescence-guided surgery also help to mark the intraoperative glioma boundary and improve the resection rate of glioma, which has been reported in China.